The present invention relates to one-way clutching or ratcheting mechanisms employed for programmer/timers employed in household washing machines and dishwashers. Programmer/timers for such appliances typically employ an electromechanical programmer which utilizes timed rotation of a cam drum for sequentially operating a plurality of electrical switches for controlling the machine functions during the program interval, which usually comprises one full rotation of the cam drum.
Electromechanical programmer/timers for appliances commonly employ an oscillating pawl and ratchet indexing mechanism for effecting timed rotation of the switch program cam drum. Alternatively or in combination therewith a continuous gear train drive with overrunning frictional clutch arrangements may be employed to permit continuous rotation of the timing motor and gear train when it is desired to stop rotation of the drum or engage an auxiliary drive mechanism for rotating the cam drum at a different rate, such as by intermittently engaging the pawl and ratchet drive. Examples of such a dual rate appliance programmer/timer cam drum drive are described and claimed in U.S. Pat. No. 4,485,096 and 4,945,196, commonly owned by the assignee of the present application.
Where it is desired to provide a one-way clutch mechanism for transmitting very small torques such as those encountered in programmer/timers for appliances, it has been found desirable to provide a "soft-touch" to the one-way clutch in the reverse or overrunning mode, and to have quiet operation of the clutch when it is overdriven, or the members are relatively rotated in a direction opposite that employed for transmitting power. It is desired to fabricate such one-way clutches from plastic material in order to provide a minimum manufacturing cost in the high volume mass production required for programmer/timer applications for household appliances.
Heretofore, plastic clutching mechanisms for appliance programmer/timers have encountered problems with deterioration of the plastic parts when subjected to exposure, over prolonged periods of time, to the operating temperatures encountered in such appliances, which typically may reach 85 degrees centigrade (85.degree. C.) Thus, it has been desired to provide a one-way clutch mechanism usable in an appliance programmer/timer which may be manufactured readily and inexpensively from molded plastic parts, and which provides a soft touch or feel in the override mode, and yet provides for reliable torque transmission in the drive mode.